The present invention relates to polyester carpets made from polyester fibers using a specific blend of fibers. It has been found that the specific blend of fibers not only improves the initial tip definition characteristics of the carpet but also increases the bulk of the carpet. In particular, the blend of fibers comprises high shrinkage copolyester fibers and low shrinkage copolyester fibers, the high shrinkage fibers having boiling water shrinkage between about 6 and 11 percent and the low shrinkage fibers having a boiling water shrinkage of less than 3 percent. The copolyester used in the fibers is a copolymer of poly(ethylene terephthalate) and a second component selected from the group polyethylene glycol, diethylene glycol and isophthalic acid. The blend of fibers generally range from 70:30 to 30:70 of the high shrinkage to low shrinkage fibers.
A major portion of the carpet used in residential and commercial establishments is the type known as saxony carpet which is a cut-pile carpet having twisted, evenly-sheared, medium length pile yarn, the yarn being in the form of individual short lengths of plied yarn (tufts.) Each tuft projects upwardly and terminates as a cut end. Yarn generally used in the saxony carpet may be nylon, acrylic, polypropylene or polyester. The present invention is directed to the area of saxony carpets containing polyester fibers.
The appearance of polyester saxony carpet is dependent on the properties of the fibers. For example, the crimp in the individual fibers imparts required cover and loftiness (i.e. firmness, resilience and body) to the carpet while the ply twist of the fibers about each other in the individual tufts gives the carpet a uniform and crisp appearance (i.e. tuft end point definition). The term tuft end point definition is used to describe the crisp appearance of the saxony carpet. It is measured qualitatively by a number of individuals reviewing the carpet. Ply twist as used herein refers to the twisting together of two or more single yarns (fibers) to form a ply yarn. The plied yarns serve to support each other. In addition, when the ply yarn is cut or sheared, it is desirous that the single yarns remain tightly together.
An important feature in the commercialization of the saxony carpets is the initial crisp appearance that customers see. However, the initial crisp appearance of saxony carpets made from conventional polyesters can be further improved by enhancing the tuft and point definition. Without good tuft definition, the tuft ends appear as if they are bloomed and visually lose the end point definition and become intermingled with the neighboring tuft ends which gives the carpet a less than desirable crisp appearance.
Efforts in the past to improve the initial tuft end point definition characteristics of polyester saxony carpet have not fully resolved the problem to the satisfaction of the carpet industry. For example, efforts have been made to increase the bulk of the carpet but at the expense of crisp appearance. Generally, when bulk is increased, the tufts are made larger which generally results in loss of end point definition.
Several approaches to improving the tuft end definition point, and in particular, to improving the initial tuft end point definition, have been disclosed in the prior art. U.S. Pat. Nos. 4,882,222 and 4,839,211 to Wilkie et al disclose a blend of fibers useful for making saxony carpet having better appearance retention characteristics made from a blend of fibers comprising low shrinkage fibers having a boiling water shrinkage of less than 12% and high shrinkage fibers being fibers having boiling water shrinkages of at least 12%. The point of the invention in Wilkie et al is directed to improving the appearance retention characteristics of the saxony carpet made therefrom. Numerous statements within the Wilkie et al patents detract from the point of the present invention. Particularly, it is stated that if the blend contains more than 40% by weight of high shrinkage fibers, the saxony carpet tends to lose its pleasing initial appearance. This is contrary to the findings of the present invention.
The claims of Federal Republic of Germany Utility Model GM 78 25 232 discloses a pile yarn made from 50-80 percent by weight of polybutylene terephthalate fibers having boiling water shrinkage of less than 5 percent and from 20 to 50 percent by weight of polyester fibers having boiling water shrinkages from 6-25 percent. Claim 1 states that the polybutylene terephthalate fiber is not limiting but further comprises polyamide, polyacrylonitrile or polypropylene fibers.
Improvements directed to tuft end point definition of polyester fibers are a continuing objective of the polyester carpet industry to meet the needs of the consumer. There remains a need to develop a polyester carpet having both good tuft end point definition and good bulk so the overall carpet is more pleasing to the consumer.